How do you know you are missing the offences? If one or other coaches are telling you, chances are their team lost(!) If both coaches say the same, ask a more experienced local referee to watch one of your games - the local FA or Referees' Association can help with that.
If you are missing possible upper body offences, two things to consider:
a) Are you too close, and looking at players' feet and ball?
b) Are you looking at players' feet and legs rather than the full picture?
Aim to be around 10-15 metres from the action (in 11-a-side) to make the full body option easier.
Well done for asking the question.